The present invention is directed to wireless communication applications, and more particularly, to techniques to synchronize to frequency hopping interfering signals in order avoid interference with such interferers.
In wireless networks, particularly short-range wireless networks such as IEEE 802.11 wireless local area networks (WLANs), the radio frequency band in which the wireless network operates is a frequency band that is shared with other wireless applications. For example, an IEEE 802.11 WLAN operates in either the 2.4 GHz unlicensed band or one of the 5 GHz unlicensed bands in the U.S. Other non-IEEE 802.11 WLAN devices operate in these frequency bands, including devices that operate in accordance with the Bluetooth™ protocol (in the 2.4 GHz band), cordless telephones (in the 2.4 and 5 GHz bands), microwave ovens, infant monitors, radar, etc. To the 802.11 WLAN devices, these other devices may be viewed as interferers. Some of interferer devices transmit signals that hop to different center frequencies throughout the frequency band on a periodic or quasi-periodic basis. When transmissions of WLAN devices overlap in frequency and time with transmissions from interferer devices, the WLAN device may suffer complete loss of signal, reduced signal quality and/or decreased throughput. Likewise, the interferer devices may suffer similar problems.
Co-pending and commonly assigned U.S. application Ser. No. 10/248,434, filed Jan. 20, 2003, entitled “Systems and Methods for Interference Mitigation with Respect to Periodic Interferers in Short-Range Wireless Applications,” discloses techniques to detect and synchronize to a periodic interferer, and to share with other devices information about a local interferer at a particular device. These techniques are useful to schedule transmissions so as to avoid the interferer only during times when it can be predicted that the interfering signal will occur in the future, but assumes that all future occurrences of the interferer, even a frequency hopping interferer, fall within a particular frequency channel of concern. It would be further desirable to be able to predict future hop frequencies of frequency hopping signals in order to schedule transmissions to avoid the frequency hopping signals only when the future hop frequencies will fall within a particular frequency bandwidth (e.g., a channel or channels).